1. Field of the Invention
The present invention relates to an Ethernet passive optical network (EPON), more particularly, to an apparatus and method for managing traffic according to subscribers, subscriber's services, and services using VLAN identification (VID) in EPON.
2. Description of the Related Art
As the next generation of an access network technology for providing fiber to the home (FTTH) and a communication and broadcasting merged service, a passive optical network (PON) technology was introduced. According to the PON technology, it can advantageously provide a broadband service that can accommodate voice, data and broadcasting in an access network, which was indicated as a bottleneck region. Therefore, it expects that the PON technology will be widely used for constructing a digital home. Relatively, 802.3ah EFM (Ethernet in the First Mile) study group was organized under a Working Group of IEEE 802 LAN/MAN standard committee, and defines EPON standard. Recently, the EFM defines an access network technology that uses three wired lines, for example, a Point-to-Point copper line, a Point-to-Point optical cable, a Point-To-Multipoint optical cable. The goals of EPON, which is the Point-to-Multipoint optical cable transmission technology, are 1 Giga-bit transmission speed, 1:16, and 10/20 Km transmission. The EPON is a shared-type optical access network that dose not require active elements such as a repeater and an amplifier of external device, minimizes the optical cable, and reduces the number of optical ports in a central office, thereby allowing affordable management. The EPON is one type of PON based on Ethernet technology.
In a conventional Ethernet protocol, a shared media connection and a point-to-point connection are only considered. On the contrary, in the EPON, a tree structure of distributed topology is formed by connecting a plurality of optical network units (ONU) or optical network terminals (ONT) to single optical link termination (OLT) based on a TDMA scheme. The ONT can be distinguished from the ONU in a view of providing a mean of directly connecting a service application terminal of a user. However, the function of the ONT is identical to that of ONU in the EPON. In the present invention, the ONU and the ONT are not distinguished. The ONU and the ONT can provide interfaces for connecting various application devices.
The EFM introduces a multi-point control protocol (MPCP) that controls the EPON in a MAC control layer.
In downlink channel, EPON always transfers Ethernet frames transmitted from an OLT to all of ONUs through a splitter. On the contrary, only OLT receives frames transmitted from one ONU in the uplink channel. Therefore, other ONUs cannot be aware of the uplink frames. That is, a problem is arisen because the EPON structure does not have a LAN characteristic using a shared medium. Accordingly, the MPCP provides a point-to-point emulation function from an ONU to other ONUs and a point-to-point communication function from an OLT to an ONU using a logical link identifier (LLID). The LLID can be allocated one or more than two for each ONU.
A time division multiple access (TDMA) is provided for an uplink channel. When an ONU transmits an Ethernet frame to an OLT, a collision of traffic may occur because a plurality of ONUs can transmit frames at the same time. In order to avoid such a collision, the MPCP provides a method of sharing the uplink channel through the TDMA.
Topological downlink traffic in the EPON can be listened by other ONUs. Also, the resource of uplink traffic can be accessed by unauthorized ONUs. Since the confidentiality of information must be provided to a subscriber and a protection service of contents and a billing service must to be provided to a service provider, the EPON must guarantee the integrity of subscriber traffic, and must block the access of unauthorized device and subscriber.
It is very important issue to manage subscriber traffic in a communication field. Many related technologies have been introduced. In general, data traffic is classified based on a given profiles according to a management purpose, and a policy is performed using the result of classification. The classification and the policy are generally performed in a L2 switch or a L3 router. Also, the packet header is inspected for the data packet classification and a matching condition is found. If a packet having a given condition is found, it is processed according to a given policing rule. A rule table stores rules according to the conditions. Generally, the switch and router manages server tens to hundreds rule tables.
FIG. 1 is a block diagram illustrating a point-to-multi-point mode EPON system according to the related art.
Referring to FIG. 1, in the EPON system, one optical link terminal (OLT) is connected to a plurality of ONUs through a splitter in a point-to-multipoint structure. A downlink transmission from the OLT to the ONU/ONTs and an uplink transmission from the ONU/ONTs to the OLT are performed based on a single transmission module that uses different wavelengths.
In order to control traffic from a switch of an OLT to subscriber devices connected to each port of ONU/OLT in the point-to-multipoint EPON, the switch of the OLT must provide a corresponding policy according to a subscriber, and a subscriber service, and a method of classifying traffic to provide the policy.
It is common to use a VID for classifying a subscriber and a subscriber service in an OLT upper layer which is a link termination device when a L2 switch or a L3 router is used in the EOPN. In this case, no method is provided for classifying subscribers connected to each ONU and a service thereof at the same time and managing them. Also, it is very difficult to manage traffic from the router to the devices connected to a plurality of ONUs due to a VID number limitation, in which the VIS number is limited to 4096.
If there are numerous subscribers and services thereof in the EPON, it is impossible to manage the traffic thereof due to the limitation of the rule table provided in the switch or the router. Therefore, it requires an additional apparatus for managing traffic from the switch or the router having insufficient classification and policy tables to an OLT MAC in order to simultaneously manage the subscriber and the service thereof.
As a related conventional technology, a traffic management apparatus for processing traffic according to a predetermine rule without using additional rule tables was introduced in U.S. Pat. No. 6,930,978. The traffic management apparatus measures the input data traffic. If the measured input data traffic is higher than a predetermined threshold value, the traffic management apparatus drops the input data traffic. On the contrary, if not, the traffic management apparatus transfers the input data traffic to a system. As described above, the traffic management apparatus can guarantee the smooth operation of the system by providing data to the system not to exceed the threshold value. However, the traffic management apparatus cannot variously and effectively manage traffic.
As another related conventional technology, a switch for controlling a rule table in real time using a CPU was introduced in U.S. Pat. No. 6,091,725. Although the switch can manage traffic in a flow unit by dynamically processing input data using the CPU and a switch, the high speed operation is impossible because of using the CPU.
As further another related conventional technology, an apparatus for integrally managing all policies through an additional policy service in a network without using a rule table was introduced in U.S. Pat. No. 6,286,052. The apparatus allows a network manager to integrally control data flows by distributing policy servers and flow information components and exchanging information using flow management sessions. However, it is impossible to variously and effectively manage the traffic according to subscriber and services thereof.